#include <stdio.h>

int main(int argc, char const *argv[])
{
    int a1 = 65 ;      //ascii 'A'
    int a2 = 'A' ;     //ascii 'A'
    int b1 = 10 ;      //ascii '\n'
    int b2 = '\n' ;    //ascii '10'

    putchar(a1);          //A
    putchar(a2);          //A
    putchar(b1);          //换行
    putchar(b2);          //换行
    putchar(a1+1);        //B
    putchar('B'+' ');     //大写转小写 + ' '     输出：b
    putchar('b'-' ');     //小写转大写 - ' '     输出：B

    return 0;
}
